<!DOCTYPE html>
<html>
	<head>
		<meta charset="utf-8">
		<title>定位</title>
		<style>
			body{
				height: 10000px;
				width:6000px;
			}
			#adv{
				width: 90px;
				border: 2px solid red;
				position: fixed;
				right: 2vw;
				bottom: 50vh;
			}
		</style>
	</head>
	<body>
		<h1>一个元素如何在另外一个元素之上</h1>
		
		<div id="adv">
			<a href="#">QQ咨询</a>
		</div>
	</body>
</html>